﻿<!DOCTYPE html>

<html lang="zh-CN">

<head>
    <meta charset="UTF-8" />
    <title>01_三角和方框的故事</title>

    <script type="text/javascript" src="../js/Oak3D_v_0_5.js"></script>

    <script id="shader-fs" type="x-shader/x-fragment">
        precision mediump float;

        void main(void) {
        gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
        }
    </script>

    <script id="shader-vs" type="x-shader/x-vertex">
        attribute vec3 aVertexPosition;

        uniform mat4 uMVMatrix;
        uniform mat4 uPMatrix;

        void main(void) {
        gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
        }
    </script>

    <script type="text/javascript">
        var gl;
        function initGL(canvas) {
            try {
                gl = canvas.getContext("experimental-webgl");
                gl.viewportWidth = canvas.width;
                gl.viewportHeight = canvas.height;
            } catch (e) {
            }
            if (!gl) {
                alert("Could not initialise WebGL, sorry :-(");
            }
        }


        function getShader(gl, id) {
            var shaderScript = document.getElementById(id);
            if (!shaderScript) {
                return null;
            }

            var str = "";
            var k = shaderScript.firstChild;
            while (k) {
                if (k.nodeType == 3) {
                    str += k.textContent;
                }
                k = k.nextSibling;
            }

            var shader;
            if (shaderScript.type == "x-shader/x-fragment") {
                shader = gl.createShader(gl.FRAGMENT_SHADER);
            } else if (shaderScript.type == "x-shader/x-vertex") {
                shader = gl.createShader(gl.VERTEX_SHADER);
            } else {
                return null;
            }

            gl.shaderSource(shader, str);
            gl.compileShader(shader);

            if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
                alert(gl.getShaderInfoLog(shader));
                return null;
            }

            return shader;
        }


        var shaderProgram;

        function initShaders() {
            var fragmentShader = getShader(gl, "shader-fs");
            var vertexShader = getShader(gl, "shader-vs");

            shaderProgram = gl.createProgram();
            gl.attachShader(shaderProgram, vertexShader);
            gl.attachShader(shaderProgram, fragmentShader);
            gl.linkProgram(shaderProgram);

            if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
                alert("Could not initialise shaders");
            }

            gl.useProgram(shaderProgram);

            shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
            gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);

            shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
            shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
        }


        var mvMatrix;
        var pMatrix;

        function setMatrixUniforms() {
            gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix.toArray());
            gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix.toArray());
        }



        var triangleVertexPositionBuffer;
        var squareVertexPositionBuffer;

        function initBuffers() {
            triangleVertexPositionBuffer = gl.createBuffer();
            gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexPositionBuffer);
            var vertices = [
                 0.0, 1.0, 0.0,
                -1.0, -1.0, 0.0,
                 1.0, -1.0, 0.0
            ];
            gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
            triangleVertexPositionBuffer.itemSize = 3;
            triangleVertexPositionBuffer.numItems = 3;

            squareVertexPositionBuffer = gl.createBuffer();
            gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
            vertices = [
                 1.0, 1.0, 0.0,
                -1.0, 1.0, 0.0,
                 1.0, -1.0, 0.0,
                -1.0, -1.0, 0.0
            ];
            gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
            squareVertexPositionBuffer.itemSize = 3;
            squareVertexPositionBuffer.numItems = 4;
        }


        function drawScene() {
            gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
            gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

            pMatrix = okMat4Proj(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0);

            mvMatrix = okMat4Trans(-1.5, 0.0, -7.0);
            gl.bindBuffer(gl.ARRAY_BUFFER, triangleVertexPositionBuffer);
            gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, triangleVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
            setMatrixUniforms();
            gl.drawArrays(gl.TRIANGLES, 0, triangleVertexPositionBuffer.numItems);

            mvMatrix = okMat4Trans(1.5, 0.0, -7.0);
            gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
            gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
            setMatrixUniforms();
            gl.drawArrays(gl.TRIANGLE_STRIP, 0, squareVertexPositionBuffer.numItems);
        }


        function webGLStart() {
            var canvas = document.getElementById("lesson01-canvas");
            initGL(canvas);
            initShaders();
            initBuffers();

            gl.clearColor(0.0, 0.0, 0.0, 1.0);
            gl.enable(gl.DEPTH_TEST);

            drawScene();
        }
    </script>
</head>

<body onload="webGLStart();">
    <canvas id="lesson01-canvas" style="border: none;" width="500" height="500"></canvas>
</body>

</html>
